An undisposed instance indicates that an instance has been collected (or at least finalized) without being properly disposed. Since the instance have been collected, having undisposed instances do not indicate a memory or resource leak. It does however indicate that the memory or resource utilization might not be optimal (e.g. by delaying the release of a resource and causing finalization of instances).

In particular, the ExecutionContext class disposes other instances in its Dispose method, so undisposed ExecutionContext instances can cause other instances to be undisposed as well, but it will not cause a memory leak. Your screenshot shows that you have a high amount of undisposed instances, but very few live instances (i.e. there's no indication of a memory leak).

If possible, you should try to make sure that all instances are correctly disposed. However, it's pretty common that the .NET Framework itself causes undisposed instances and there's nothing you can do about it.